According to a conventionally known method for manufacturing these kind of imaging elements, a metal mold having arranged tubelike units is formed by nano-processing and the neighboring two surfaces (the sides corresponding to the mirror surfaces of the micro holes) of the tubelike units are processed into mirror surfaces with a plane roughness of not larger than 50 nm, which are reversed and transferred by nano-imprinting or electrocasting using the mold for forming a plurality of micro through-holes with a predetermined pitch on the substrate. (Refer to International Publication No. WO 2007/116639 (paragraph 0032, in particular)).